The invention relates to an electromagnetically operated hydraulic control valve having a valve housing in which a series of valve bodies are disposed for longitudinal displacement in bores between at least two control positions, and having a pot electromagnet disposed on the valve housing and an armature provided between the pot electromagnet and the valve housing in the form of a substantially flat disk to which one or more of the extremities of the valve bodies projecting from the valve housing are attached.
The electromagnetic operation of hydraulic control valves, in which the armature of an actuating electromagnet disposed on the valve housing operates a valve body in the form of a longitudinal slide or "spool", is known, at least one operating electromagnet being associated with each spool when the return of the spool is accomplished by spring power. Also, the arrangement of two electromagnets acting on the opposite ends of the spool is used whenever the return of the spool or its shift to another control position (in the case of a three-position control valve) is accomplished by magnetic actuation. Control valves having complex functions for which a plurality of valve bodies are provided for synchronous actuation are in most cases provided with at least one actuating electromagnet for each valve body or spool, the synchronous actuation being accomplished by the simultaneous energizing of the electromagnets associated with a particular control function. Particularly when the valve control consists of seated valves, which in contrast to the common longitudinal spools cannot easily be combined to form a single valve body by arranging a plurality of seated valves axially in tandem, but must be disposed and actuated separately, the technical expense and the amount of space required is increased by the large number of actuating electromagnets then required. On the other hand, however, seated valves are particularly desirable for use in very high pressure hydraulic control systems, because high-efficiency systems of relatively small dimensions and weights can thus be created.
In a known four-way valve of the kind mentioned in the beginning (U.S. Pat. No. 3,251,378), a reduction of the technical cost is achieved by the fact that, instead of the individual actuating electromagnets associated with each valve body, a single pot electromagnet with a plate-like armature is provided, to which shafts of the two valve bodies extending from the valve housing are connected. In hydraulic control valves of complex functions, in which more than two valve bodies must be operated simultaneously at each stroke, it is important especially in the case of high pressure and very high pressure systems, that the operation of the individual valve bodies, i.e., the opening and the closing thereof, be performed with good synchronism. Even slight timing errors in the opening and closing action of cooperating valve bodies can otherwise--even if the individual valve bodies are carefully relieved of hydraulic pressure--give rise to the development of hydraulic pressure fluctuations and vibrations. Since the plate armature in the known four-way valve is disposed loosely between the valve housing and the pot electromagnet, there is no way of preventing it from tilting slightly due to variations in the resistance of individual valve bodies to shifting, with the result that precisely synchronous actuation cannot be achieved.